Method and apparatus for sunless tanning

ABSTRACT

Apparatus for simulating skin tanning comprises a receptacle containing a fluid comprising dihydroxyacetone, a receptacle containing a fluid comprising a secondary polyamine, and dispensing means for simultaneously or sequentially providing desired amounts of dihydroxyacetone and polyamine.

The present application is the United States national application corresponding to International Application No. PCT/US 93/11906, filed Dec. 14, 1993 and designating the United States, which PCT application is in turn a continuation-in-part of U.S. application Ser. No. 07/991,666, filed Dec. 16, 1992, now abandoned, the benefit of which applications are claimed to the provisions of 35 U.S.C. 120, 363 and 365 (C).

FIELD OF THE INVENTION

This invention relates to a method and apparatus which are useful in the simulated tanning of skin. More particularly, the invention relates to the treatment of skin with dihydroxyacetone compositions, to form a brownish coloration thereon.

INTRODUCTION TO THE INVENTION

It has long been known that certain compounds form pigments when applied to the skin. Products containing dihydroxyacetone (frequently simply abbreviated "DHA") have been marketed since the early 1960's, and have been found satisfactory by many persons who wish to give their skin the appearance of an attractive tan, but do not desire to risk the now well-appreciated health hazards of exposure to solar or artificially-generated ultraviolet radiation.

However, some persons have not obtained the desired results from DHA applications. A small number of individuals develop a coloration which tends to appear yellowish or orange. Some others, probably due to perspiration, rubbing or washing during the slow generation of color as skin components react with DHA, or to a lack of care to evenly apply the DHA, develop uneven coloration.

The chemistry of DHA-skin interaction has been investigated by several workers. Wittgenstein and Berry published a paper "Reaction of Dihydroxyacetone (DHA) with Human Skin Callus and Amino Compounds," in The Journal of Investigative Dermatology, Vol. 36, pages 283-286 (1961), describing work to characterize the browning phenomenon. They reported that DHA reacts with a number of compounds, including ammonia and amino acids, to form a brown color, and theorized that skin browning is due to the reaction of DHA with free amino groups in the skin, the amino groups probably being on arginine molecules which are present in skin proteins.

A. Meybeck published "A Spectroscopic Study of the Reaction Products of Dihydroxyacetone with Aminoacids" in Journal of the Society of Cosmetic Chemists, Vol. 28, pages 25-35 (1977), and characterized brown pigments formed from the reaction of DHA with amino and other acids at 100° C. Further experiments at 37° C. were conducted to better simulate reactions which may occur in the skin: DHA was reacted with the amino acids glycine, lysine, alanine, serine and arginine, but only glycine and lysine produced significant amounts of pigment after 24 hours. It was concluded that DHA must act by initially condensing with free amino acids at the skin surface, followed by polymerization and linking to proteins in the stratum corneum, probably through lysine side chains.

A further study was reported by M. F. Bobin, M. C. Martini and J. Cotte, "Effects of Color Adjuvants on the Tanning Effect of Dihydroxyacetone," Journal of the Society of Cosmetic Chemists, Vol. 35, pages 265-272 (1984). This work involved measuring the rate of color development after mixing DHA and various amino acids or their derivatives, and applications of DHA and methionine sulfoxide in vivo. It was concluded that methionine sulfoxide is a useful adjuvant to DHA, as the combination provided rapid color development, plus a more intense and long lasting color than would be obtained with only DHA. This result was thought to result from the affinity of methionine sulfoxide for keratin.

Chemical Abstracts, Vol. 95, abstract 30226 g (1981) summarizes a German patent document (3,037,497) pertaining to dyeing skin, hair, feathers, fur, etc. by treating with a mixture of DHA and an amino acid sulfoxide. When DHA and methionine sulfoxide were applied in cream formulations, skin turned a deep brown color after three hours and the color was more resistant to washing than that obtained with only DHA.

Black et al., in U.S. Pat. No. 3,177,120, discussed the problem of including DHA and amino group-containing sunscreens together in a formulation, and concluded that only sunscreens free from amino groups should be used, to prevent formation of a yellow or brown color in the storage container; color formation is also said to be accompanied by inactivation of both the DHA and sunscreen.

In spite of the teachings in the art relating to the use of DHA with α-amino acids and their derivatives, it has been found that color formed thereby does not have a desired substantivity, or resistance to removal by rubbing or washing. Thus, it is desired to provide apparatus and a method for browning skin to form simulated tans having improved substantivity and colors which closely resemble those obtained from exposure to ultraviolet radiation.

SUMMARY OF THE INVENTION

The invention, in one aspect, provides an apparatus for imparting artificial tan to skin, comprising: a receptacle containing a fluid formulation comprising dihydroxyacetone; a receptacle containing a fluid formulation comprising a secondary polyamine; and dispensing means for simultaneously or sequentially providing desired amounts of dihydroxyacetone and polyamine. The invention also includes a method for imparting artificial tan to skin, comprising simultaneously or sequentially contacting the skin with dihydroxyacetone and a secondary polyamine. Also included is a composition for immediate application to skin, comprising dihydroxyacetone, at least one secondary polyamine and a suitable carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a pouch container having two compartments.

FIG. 2 is a cross-sectional view of a squeeze bottle having two compartments.

FIG. 3 is a cross-sectional view of a dual-compartment tube container.

FIG. 4 is a cross-sectional view of a container having two compartments and a dual pump dispenser.

FIG. 5 is a cross-sectional view of a dual-compartment pressurized dispensing container.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described with reference to the accompanying drawings. In the description and claims, all percentages are expressed on a weight basis, unless otherwise noted.

In accordance with the invention, there is provided apparatus for imparting a simulated tan to skin, the apparatus having separate compartments for a formulation containing dihydroxyacetone and a formulation containing a secondary polyamine. As previously noted in the art, it is important to prevent the mixing of the components until a user is ready to make a skin application, to prevent premature reaction and color formation. The apparatus can be configured to simultaneously dispense the formulations, in desired amounts, or to sequentially dispense them. If sequentially dispensed, the formulations can be mixed before spreading onto the skin, or can be spread in the order of dispensing.

Referring to FIG. 1, there are shown the features of a two-compartment pouch 10. Included is septum 12 which, in the least complex embodiment where the pouch comprises heat sealed layers of a thermoplastic substance, is merely a heat sealed seam to divide the volume of the pouch. This septum divides the volume into chambers 14 and 16. Tearing notch 18 can be provided to facilitate removal of the top of the pouch, when it is desired to dispense formulations contained therein. This embodiment will be used primarily for single-use quantities, the pouch holding an appropriate quantity for application once to the whole body or a portion thereof, such as only the face.

As an alternative to a tearing notch, the user can simply cut off the top of the pouch with scissors or a knife. Further, rather than dispensing the two formulations from the pouch in two streams, as would be done with the configuration depicted, septum 12 can be made frangible; applying pressure with the fingers to one side of the pouch will rupture the septum and permit mixing of the formulations by sequentially applying pressure to the two sides, after which a single composition containing both DHA and polyamine can be applied. Of course, such mixing should only be conducted immediately before use.

For sequential application of the two formulations, another tearing notch (not shown) can be provided on the opposite side of the pouch from notch 18, and the septum can be extended to the uppermost limit of the pouch. This will permit only one compartment to be opened by pulling above a notch.

FIG. 2 is a view of a squeeze bottle 20, which is provided with septum 22 to form two compartments 24 and 26. The bottle is conveniently formed by molding with thermoplastic substances, as is well known in the art. In a typical embodiment, threads 34 will be provided for closure with a conventional screw cap (not shown). The threads will not be needed if the bottle is closed by alternative means, such as a pressed on flip cap.

Preferably, gripping indentations 28 are provided, to ensure that the bottle is squeezed in locations which will apply approximately uniform pressure to the two compartments, i.e., not to a less deformable area such as that directly over the septum. Upon pressure application, formulations are dispensed from the compartments through orifices 30 and 32.

The bottle can be used for sequential applications of DHA and polyamine, by providing separate closures for the two orifices. As an example, individual snap caps can be provided over the orifices. The user would be required to dispense an appropriate amount of a component, rub that component into the skin and, immediately or after a prescribed time, apply the second component to the skin in a similar manner. Application of equal amounts of the components can be accomplished with sufficient accuracy by noting the lengths of dispensed fluids on the skin; the bottle can be provided with length scales marked thereon to make this more convenient.

Referring now to FIG. 3, there is shown a cross-sectional view of a collapsible tube assembly 36 which is useful in the invention. As shown, the outer tube 38 surrounds the inner tube 40, and contents of the outer and inner tubes can be discharged through outlets 42 and 44, respectively, by squeezing the assembly. A threaded area 46 is provided for attachment of a closure (not shown). Any desired number of outlets can be provided for the tubes and any desired type of closure can be used, the invention not being restricted to a threaded cap.

The assembly can be fabricated from any materials normally utilized for tubes dispensing medications, cosmetic materials, hygiene products such as toothpastes, cleaning compositions and the like, subject to the usual requirement that the materials of construction do not react with formulations contained therein to an appreciable extent during at least the expected storage term. Frequently used materials include metals, polymers and composites, including laminates. Typically, the assembly will be closed at its bottom end by crimping or heat sealing, depending upon the materials of construction. To assure that formulations are dispensed in predetermined relative amounts from the outer and inner tubes, means (not shown) such as a key can be provided at the bottom of the assembly for uniformly collapsing the tubes; as the bottom of the assembly is wound around a rotated key, approximately the same pressure will be applied to the two tubes.

A further apparatus is shown in cross-section as FIG. 4. In this figure, dispensing container 48 comprises bottle 50, having dividing septum 52 which forms two compartments 54 having any desired geometry. Cap 56 is adapted to fit over the outlets of pumps 58, mounted to close the compartments and which can be any of the well-known spring loaded check valve pumps such as are used with hand lotions and other cosmetic products. Pressing down on the cap causes formulations to be simultaneously dispensed from conduits 62; releasing the cap permits it to rise under pressure from springs in the pumps, simultaneously reloading the pumps with stored formulations through dip tubes 60.

This apparatus requires no particular care on the part of the user to obtain a correct ratio of the formulations, in cases where the formulations are to be simultaneously dispensed and applied, but permits complete separation of the components until dispensing. By providing separate caps over the pumps, it would be possible to dispense the formulations at different times, should this be desired. In either embodiment, reproducible amounts will be dispensed simply by pressing the cap down for its full length of travel each time, without any need for a user to make measurements.

FIG. 5 relates to a pressurized aerosol container which can be used to dispense two components simultaneously. Container 64 comprises external shell 66, with bottom closure 68 attached; preferably, both of these components will be fabricated from metals, with the bottom closure crimped or welded to the shell. Gas filling port 70 is provided to seal the container after a pressurizing gas is introduced.

The container is divided by barrier 72, which is provided with one or more perforations 74 near the bottom of the container, to equalize gas pressure in the two sections formed by the barrier. Each section has an accordion-pleated bag 76, preferably fabricated from a plastic material, to contain a formulation, the bags each being connected to an aerosol valve 78 which is actuated to release formulation by its depression into the container. Cap 80 is utilized to simultaneously depress the valves, and directs formulations through conduits 82 for application to a desired area.

This apparatus has the advantages of dispensing desired relative amounts of the contained formulations without any special care on the part of the user, and being very simple to use. By using plastic bags to contain the formulations, the aerosol container needs not be chemically compatible with the formulations, and the propellant will not normally be in contact with the formulations. Of course, costs can be reduced by changing the design to make use of sealed compartments having pistons driven by gas pressure to force formulations out through the valves, but piston sealing, compatibility of construction materials with the formulations and other considerations will complicate the product design. Many alternatives will be apparent to those skilled in aerosol container packaging.

Another useful package for the present invention has two compartments, divided by a removable or frangible barrier. An example is the collapsible tube of U.S. Pat. No. 2,176,923 to Nitardy, where two substances are separated in a tube by a transverse partition which is a collapsible disk having a central aperture; expressible plugs in the aperture are removed by applying pressure to the bottom of the tube, causing the substances to mix. U.S. Pat. No. 3,290,017 to Davies et al. is related, having a disc which can be moved from a barrier position to a mixing position in a tube by external finger pressure.

A further example is found in U.S. Pat. No. 3,608,709 to Pike, where a multiple-compartment laminated pouch is described. This pouch, when external pressure is applied, will form a single compartment by breakage of the internal barrier, permitting two formulations contained therein to mix. Other packages having frangible internal barriers are shown in the following U.S. Pat. Nos. 3,756,389; 4,458,811; and 4,608,043; these can be adapted for use in the present invention.

U.S. Pat. No. 3,809,224 to Greenwood shows another useful package, having an external clamp divider seal which can be removed to permit mixing of components stored separately when the clamp is in place.

Each of these packages having a frangible or removable barrier will be suitable for single use unit packaging only, since it will be necessary to use the entire contents of the package promptly after the DHA and polyamine formulations are mixed, due to the previously discussed reaction.

U.S. Pat. No. 5,137,178 to Stokes et al. describes a dual tube dispenser which is actuated by simultaneously squeezing buttons located in opposing sides of a rigid shell, each button compressing an underlying flexible compartment, to expel two separate components through closely spaced orifices located on an end of the dispenser.

The foregoing is a description of representative packaging techniques for maintaining and dispensing a formulation comprising dihydroxyacetone and a formulation comprising a secondary polyamine. Both formulations must be fluid, that is, capable of flow under the influence of gravity or a moderate externally applied pressure. Examples of useful fluid formulations are ointments, dispersions such as creams and lotions, gels, solutions, and the like, each of which (and preparative techniques therefor) are very well known to those skilled in the formulating art.

Typically, both formulations which are to be used together will be of the same type, e.g., if one is a gel, the other also will be a gel to facilitate application and mixing. However, it is not always necessary to observe this general principle.

Polyamines which are useful in preparing the formulations of the invention either: have the general formula R¹ NH(CH₂)₂ NHR², where R¹ and R² are independently hydrogen, or alkyl, cycloalkyl or aromatic (including substituted aromatic) groups having up to about 22 carbon atoms, provided that both of R¹ and R² cannot be hydrogen; or have the general formula (CH₂ CH₂ NH)_(n), where n is an integer from about 3 to about 15000; or have a silicone backbone.

The terms "alkyl," "cycloalkyl" and "aromatic" are used herein to refer to substituted or unsubstituted groups, branched or unbranched, with permissible substituents including hydrocarbon groups, halogen or halogen-containing groups, nitrogen-containing groups, sulfur-containing groups, hydroxy or hydroxy-containing groups, carbonyl or carbonyl-containing groups, and the like. In many instances, the groups will be purely hydrocarbon groups.

Useful compounds also include those having a silicone backbone, such as amodimethicone and trimethylsilylamodimethicone, available from Dow Corning Corporation, Midland, Mich. U.S.A. and reported to have the following structures, where R is lower alkyl (i.e., having 1 to about 8 carbon atoms) and x and y may be varied over a wide range to provide the compounds with desired properties. According to U.S. Pat. No. 4,888,368 to Kohl et al., amodimethicone is characterized by values of x from 500 to 520 and values of y from 2 to 2.3. According to U.S. Pat. No. 4,960,588 to Hoshowski et al., trimethylsilylamodimethicone products have values of x+y from 50 to 500, the mole percent of amine functionality varies from 1 to 5, and R has 2 to 5 carbon atoms. ##STR1##

For amodimethicones and trimethylsilylamodimethicones to be used in the present invention, suitable values of x range from 1 to about 500 and suitable values of y range from 1 to about 100. For trimethylsilylamodimethicones, presently preferred values of x+y range from 2 to about 500 and the mole percent of amine functionality ranges from about 1 to about 60. Examples of preferred trimethylsilylamodimethicones are the compound having x about 100 and y about 32, and the compound having x about 25 and y about 8.

Many variations of the amodimethicone and trimethylsilylamodimethicone compounds are useful in the invention. For amodimethicone, either or both of the methyl groups can be replaced with a lower alkyl group, and the ethylene group can be replaced with a lower alkylene group. In trimethylsilylamodimethicone, these same substitutions can be made for any of the methyl and ethylene groups shown therein. In a given molecule, not all of the groups shown in a given position in the structure must be the same lower alkyl or lower alkylene moiety; for example, a fraction of the ethylene groups may be replaced by propylene groups. For purposes of this invention, any of these compounds are considered to be amodimethicones or trimethylsilylamodimethicones, depending upon which structure they most closely resemble.

Other useful compounds having a silicone backbone include those having the following structure: ##STR2## where R¹, R², R³ and R⁴ are independently lower alkyl, having from 1 to 8 carbon atoms, and x is less than about 100. Preferably, x is 1 to about 50. It is also preferred that R¹ is an ethylene group. Individual lower alkyl groups having the same identifier in the formula need not be the same; for example, one or more of R³ groups can be ethyl while one or more of the others are propyl. A very useful compound represented by this formula has R¹ groups which are ethylene, R² groups which are propylene, R³ groups which are ethyl and R⁴ groups which are methyl, with x being about 8.

Secondary polyamines for use in the present invention include N-substituted ethylenepolyamines, N,N'-disubstituted ethylenepolyamines or polyethyleneimines. It is important that the polyamine has at least one secondary amino group. Tertiary amino groups do not appear to react with DHA. In general, it has been found that N-substituted ethylenepolyamines generate browning end products with dihydroxyacetone somewhat more quickly, and in higher yields, than either of N,N'-disubstituted ethylenepolyamines or primary amines.

In general, the substituent for an N-substituted ethylenepolyamine will preferably have about 6 to about 22 carbon atoms. A symmetrical N,N'-disubstituted ethylenepolyamine preferably will have about 4 to about 22 carbon atoms in the substituent group. Other N,N'-disubstituted ethylenepolyamines preferably will have one substituent group with about 6 to about 22 carbon atoms, while the other preferably has 1 to about 22 carbon atoms.

Suitable polyethyleneimines for the present invention include those having a very wide range of ethyleneimine repeating units, as noted above. Several representative compounds are listed in CTFA Cosmetic Ingredient Handbook, published by The Cosmetic, Toiletry and Fragrance Association, Inc., Washington, D.C., U.S.A., as having the following composition, where n is the variable in the formula (CH₂ CH₂ NH)_(n) :

    ______________________________________                                         CTFA           CAS Registry                                                    Designation    Number     n                                                    ______________________________________                                         PEI-15         9002-98-6  15                                                   PEI-30         9002-98-6  30                                                   PEI-45         9002-98-6  45                                                   PEI-275        9002-98-6  275                                                  PEI-700        9002-98-6  700                                                  PEI-1000       9002-98-6  1000                                                 PEI-1400       9002-98-6  1400                                                 PEI-1500       9002-98-6  1500                                                 PEI-1750       9002-98-6  1750                                                 PEI-2500       9002-98-6  2500                                                 PEI-14M        68130-97-2 15000                                                ______________________________________                                    

Preferably, n will be from about 3 to no greater than about 2500 for use in the present invention.

Volumes and active ingredient concentrations of dispensed formulations should be chosen to provide molar ratios of DHA to polyamine about 0.1 to about 14. More preferably, the ratios should be about 0.5 to about 5. Still more preferred are molar ratios about 2 to about 4. If the number of moles of DHA exceed the number of moles of polyamine, a portion of the DHA will remain free to react with amino groups in the skin, increasing the substantivity of the color formed; thus, a molar excess of DHA is preferred. Although the rate of color formation in the skin (with free amino groups present there) is considerably slower than that of DHA with provided secondary polyamine on or near the skin surface, color formed in the skin is more resistant to removal by washing and abrasion. For this reason, it is preferable to establish both the early and frequently more intense color on the skin surface, and the more permanent but slower forming color in the skin layers.

It has been found that pH at the time of application affects the resulting color. In general, either the DHA formulation or the polyamine formulation should be able to establish pH values about 3 to about 13 locally when applied to the skin. More preferred are values about 5 to about 9, with values about 6 to about 7 being particularly preferred with most formulations. The optimal pH for a given polyamine application will be somewhat dependent upon the pK_(a) of that polyamine, and can be easily determined by applying formulations having different pH values to the skin.

To compare simulated tans created by different means, it is helpful to have an objective, instrumental measurement of colors and intensities. Accordingly, a method has been developed using a Minolta Chroma Meter CR-200, which uses reflected light from a surface and gives results in terms of the CIE (International Commission on Illumination) tristimulus values. These values are subsequently transformed mathematically into the L, a* b* color space, wherein the magnitudes of changes in hue and intensity of color correspond closely with those perceived by the human eye.

L*, being achromatic, ranges from black (L*=0) to white (L*=100); this term is called "metric lightness" and is a measure of how light or dark a color is, relative to a matching shade of gray. Hue is measured in terms of the chromaticity coordinates a* and b*, where a* indicates redness (a*>0) and b* indicates yellowness (b*>0). The values of a* and b* can be plotted with a* as the x-axis and b* as the y axis, to give quantitative color information: "metric chroma" is the length of a line from the origin (a*=0, b*=0) to the point of a sample reading, while "metric hue angle" is the angle between the a* axis and the metric chroma line. Metric chroma indicates the strength of a color response (i.e., the extent to which a color differs from its matching shade of gray). Metric hue angle quantifies hue in degrees, with larger values indicating more yellow hues and smaller values indicating more red (or less yellow) hues.

The meter is used to measure natural tans with a number of subjects, to establish a target for the appearance of tans produced by DHA reactions. In general, it is found that points on a chromaticity plot for dark tans will have b* from about 19 to about 24, with a* ranging from about 10 to about 14. For medium tans, b* will be about 20 to about 24, with a* from about 9 to about 12. For light tans, b* will be about 18 to about 20, with a* about 7 to about 10. Rather than being a point, the target color is represented by the area on the plot where natural tans lie. Values of metric chroma increase steadily as tans progress from light to medium, but increase much more slowly as tans become more dark than "medium." In contrast, values of metric hue angle overlap significantly for light, medium and dark tans, except for very dark tans which have increased redness (decreased metric hue angle).

Metric lightness is the third required parameter for characterizing natural tans. L* values decrease as tans become darker, a difference Of about one unit being discernable to a trained observer. For natural tans, L* ranges from about 47 to about 53 for dark tans, about 54 to about 57 for medium tans and about 58 to about 64 for light tans.

The meter is also used to measure the characteristics of simulated tans obtained using only DHA applications. Several subjects are treated with an oil in water emulsion containing 5 percent DHA, with applications (2 mg DHA/cm²) being made once each day for four days. After the first day, values for b* are about 13 to about 21, the a* values are about 3 to about 8 and L* values are about 63 to about 74. After two days, b* is about 15 to about 23, a* is about 5 to about 8 and L* is about 62 to about 72. After the third day, b* is about 16 to about 23, a* is about 5 to about 9 and L* is about 61 to about 71. After four days, b* is about 17 to about 24, a* is about 5 to about 9 and L* is about 61 to about 70. The hues for all but a few of the readings are more yellowish than the tan target area, and all but a few of the readings indicate tans more light than natural tans, even though comparable levels of metric chroma are generated. It can generally be stated that simulated tans using only DHA are more yellow and lighter than natural tans having similar extents of color formation.

The following examples are provided to illustrate various aspects of the invention, and are not to be construed as limiting the invention in any manner.

EXAMPLE 1

Secondary polyamines are tested to confirm their ability to form browning end products with dihydroxyacetone, by placing 25 μl each of polyamine solution and DHA solution onto the same spot of a silica gel thin layer chromatography plate. Browning can be visually observed against the white background of the plate. The polyamine solutions are 0.55 molar and the solvent is water, unless the polyamine is identified with one or more asterisks in the following table, adjusted to pH values about 9 with dilute hydrochloric acid or sodium hydroxide solution, as required. The DHA is 1.1 molar in water solution. A single asterisk following the name of a polyamine indicates that the compound is dissolved in 50 percent aqueous ethanol, while a double asterisk indicates a solution in 95 percent ethanol. Each listed polyamine yields a suitable brown coloration in the test.

N,N'-dimethylethylenediamine

N,N'-diethylethylenediamine

N,N'-diisopropylethylenediamine

N,N'-di-n-propylethylenediamine

N,N'-di-n-butylethylenediamine *

N,N'-di-n-hexylethylenediamine **

N,N'-dibenzylethylenediamine **

N,N'-di-(2-carboxyethyl)-ethylenediamine

N,N'-di-(2-hydroxyethyl)-ethylenediamine

Polyethyleneimines of the formula (CH₂ CH₂ NH)_(n) :

    ______________________________________                                         Epomin SP-012 ™    n = 30                                                   Epomin P-1000 ™    n = 1750                                                 Polymin G 35 ™     n = 35                                                   Polymin FG ™       n = 10                                                   Polymin P ™        n = 15000                                                ______________________________________                                    

The Epomin™ products are available from Aceto Corporation, Flushing, N.Y., U.S.A.; the Polymin™ products are available from BASF Corporation, Parsippany, N.J., U.S.A.

EXAMPLE 2

The test of the preceding example is conducted with solutions of the following polyamines, each of which yields a suitable brown coloration. In the list, the asterisks following a compound have the same meaning as in Example 1.

N-ethylethylenediamine

N-n-propylethylenediamine

N-isopropylethylenediamine

N-n-butylethylenediamine

N-sec-butylethylenediamine

N-hexylethylenediamine *

N-phenylethylenediamine

N-benzylethylenediamine

N-(2-hydroxyethyl)-ethylenediamine

N-(3-hydroxypropyl)-ethylenediamine

N-[3-(trihydroxysilyl)-propyl]-ethylenediamine *

N-[3-(trimethoxysilyl)-propyl]-ethylenediamine *

Amodimethicone **

Trimethylsilylamodimethicone **

N-naphthylethylenediamine

EXAMPLE 3

A test is conducted to compare the browning reactions of N,N-diethylethylenediamine (tertiary amine) with those of N-ethylethylenediamine (secondary amine), each compound also having a primary amino group. Reactions are carried out in aqueous solutions which are 0.05 molar in both amine and DHA, and containing 0.5 molar phosphate buffers which maintain pH values about either 7 or 9. After seven hours of reaction at 20° C., absorbance of the reaction product in the aqueous solutions is measured spectrophotometrically in a 1.0 cm cell at a wavelength of 500 nm, giving results as in the following table.

    ______________________________________                                         Amine           pH    Absorbance                                               ______________________________________                                         Tertiary        7     0.0300                                                                   9     0.0625                                                   Secondary       7     2.4324                                                                   9     2.3916                                                   ______________________________________                                    

The difference shown in reaction product absorbance (assumed to be directly proportional to concentration) indicates that the primary amino group present in each molecule is not the more significant reactive moiety of these polyamines. Since the tertiary amino group in N,N-diethylethylenediamine does not participate in the browning reaction, and since the pK_(a) values for the primary amino groups of the two amines are not significantly different, there is strong evidence that the secondary amino group of the N-ethylethylenediamine participates directly in the browning reaction.

EXAMPLE 4

A gel containing polyamine is prepared, using the following components:

    ______________________________________                                         70.5     grams       Alcohol SD40-2                                            4        grams       N-hexylethylenediamine                                    21       grams       Water                                                     1.5      grams       Hydroxypropylcellulose                                    3        grams       Hydrochloric acid, 6N                                     ______________________________________                                    

The gel is prepared by dissolving the amine in the alcohol, slowly adding the water, with stirring, to obtain a clear solution, adding the hydroxypropylcellulose with mixing, continuing mixing until the mixture is free of lumps, and adding the hydrochloric acid to obtain pH values of 9 to 9.5.

The hydroxypropylcellulose is sold as Klucel HF™ by Hercules Inc., Wilmington, Del. U.S.A.

EXAMPLE 5

A gel containing a polyamine is prepared, using the procedure and components of the preceding example, and the following amounts:

    ______________________________________                                         70.0     grams       Alcohol SD40-2                                            8.0      grams       N-hexylethylenediamine                                    13.5     grams       Water                                                     1.5      grams       Hydroxypropylcellulose                                    7.0      grams       Hydrochloric acid, 6N                                     ______________________________________                                    

EXAMPLE 6

A gel is prepared from the following components:

    ______________________________________                                         Part    Grams          Component                                               ______________________________________                                         A       65.45          Water                                                           1.44           Polyquarternium-10                                      B       19.16          Alcohol SD40-2                                          C       0.17           Water                                                           0.02           Citric acid                                             D       4.78           Water                                                           7.10           Dihydroxyacetone                                                0.10           d,l-Panthenol                                                   0.05           Aloe concentrate                                        E       1.44           Polysorbate-80                                                  0.29           Fragrance                                               ______________________________________                                    

The gel, containing 7.10 percent DHA, is prepared by adding the Polyquarternium-10 to the water of part A, with stirring until the mixture is thick (about one hour). The alcohol of part B is added slowly, with stirring, to the part A mixture to form a uniform gel. Citric acid is dissolved in the water of part C, then mixed into the gel. The part D ingredients are dissolved in the water of that part, then mixed into the gel. Finally, the fragrance and Polysorbate-80 are mixed, and combined with the gel.

To 50 grams of the foregoing gel are added 21 grams of 50 percent (in water) Alcohol SD40-2, to prepare a gel containing 5 percent DHA.

The polyquaternium-10 is available from Amerchol Corporation, Edison, N.J. U.S.A. as Ucare Polymer JR-30M™. The polysorbate-80 is sold by ICI Americas Inc., Wilmington, Del. U.S.A. as Tween 80™.

EXAMPLE 7

A gel containing 10 percent DHA is prepared using the following components:

    ______________________________________                                         Part    Grams          Component                                               ______________________________________                                         A       53.30          Water                                                           1.50           Polyquaternium-10                                       B       20.00          Alcohol SD40-2                                          C       0.18           Water                                                           0.02           Citric acid                                             D       15.00          Water                                                           10.00          Dihydroxyacetone                                        ______________________________________                                    

The polymer of part A is slowly added, with constant stirring, to the water of that part; mixing is continued until the mixture is thick. Alcohol of part B is slowly mixed into the thick mixture. Citric acid is dissolved in the water of part C and stirred into the mixture. Finally, the DHA is dissolved in the water of part D and combined with the mixture. The polyquaternium 10 can be obtained from Amerchol Corporation as Ucare Polymer JR-30M™.

EXAMPLE 8

A lotion is prepared using the following components:

    ______________________________________                                         Part    Grams         Component                                                ______________________________________                                         A       63.32         Water                                                    B       10.00         Emulsifying wax                                          C       8.00          N-hexylethylenediamine                                           10.00         Propylene glycol                                         D       7.28          Water                                                            1.40          Citric acid                                              ______________________________________                                    

The water of part A is heated to 70° C., and the wax of part B is heated to 70° C. The heated components are combined, with rapid mixing, and cooled to 45° C. with mixing. The N-hexylethylenediamine is mixed into the propylene glycol, then the mixture is combined with the previous components. The combination is cooled to 35° C. The citric acid of part D is dissolved in the water of that part, and the solution is added to the preceding components, to adjust the pH of the composition to about 9.0 to 9.5.

The emulsifying wax is sold as Polawax™ by Croda Inc., New York, N.Y. U.S.A.

EXAMPLE 9

A lotion is prepared, using the following components:

    ______________________________________                                         Part   Grams       Component                                                   ______________________________________                                         A      64.00       Water                                                       B      15.00       Emulsifying wax                                                    1.00        n-Hexadecyl alcohol                                                2.00        Polyoxyethylene(10)oleyl ether                              C      8.00        N-hexylethylenediamine                                      D      1.75        Citric acid                                                        5.00        Water                                                       E      3.25        Water                                                       ______________________________________                                    

The water of part A is heated to 70° C. The components of part B are heated to 70° C. The heated components are combined, with vigorous mixing, and cooled to 45° C. N-hexylethylenediamine is added and mixed vigorously. The citric acid is dissolved in the water of part D and added to the preceding components, to obtain a pH about 9. The water of part E is then combined with the other components.

The emulsifying wax is Polawax™, sold by Croda Inc. The polyoxyethylene(10)oleyl ether is sold by ICI Americas Inc., Wilmington, Del. U.S.A. as Brij 97™.

EXAMPLE 10

A lotion is prepared, using the following components:

    ______________________________________                                         Part   Grams      Component                                                    ______________________________________                                         A      60.20      Water                                                               1.18       Polyoxyethylene(10)cetyl ether                               B      6.50       Polyoxyethylene fatty alcohol ethers                                0.82       Polyoxyethylene(2)cetyl ether                                       0.30       n-Hexadecyl alcohol                                                 5.00       Isopropyl palmitate                                          C      15.00      Water                                                               10.00      Dihydroxyacetone                                             D      1.00       Biocide                                                      ______________________________________                                    

The part A components are mixed and heated to about 75° C. The part B components are mixed and heated to about 75° C. to form a solution. Parts A and B components are combined with vigorous mixing, then cooled to about 50° C. The DHA is dissolved in the water of part C, and combined with preceding components. Finally, the biocide is mixed into the preparation.

The polyoxyethylene(10)cetyl ether and polyoxyethylene(2)cetyl ether are sold by ICI Americas Inc., Wilmington, Del. U.S.A. as Brij 56™ and Brij 52™, respectively. The polyoxyethylene fatty alcohol ethers are sold by Amerchol Corp., Edison, N.J. U.S.A. as Promulgen G™.

EXAMPLE 11

Substantivity to water rinsing indicates, at least partly, the water solubility of the color formed. A suitable test involves measuring skin color with the Minolta Chroma Meter, applying formulations to the skin, allowing color to develop for about five hours, then repeating the color measurement. A gentle stream of luke-warm tap water is allowed to flow over the treated skin for two minutes, then the skin is dried by gently patting with dry paper towels. A final skin color measurement is then taken, thirty minutes later. Values of ΔE, which represents total color difference between treated and untreated skin, can be calculated from the following equation:

    [(L*.sub.U -L*.sub.T).sup.2 +(a*.sub.U -a*.sub.T).sup.2 +(b*.sub.U -b*.sub.T).sup.2 ].sup.1/2

where the subscripts "U" represent readings with untreated skin and the subscripts "T" represent readings with treated skin.

The following results are obtained with various amines plus DHA, as compared with DHA only. The amine "TSPE" is 25 μl of a 2.5 percent solution of N-[3-(trihydroxysilyl)-propyl]-ethylenediamine in 50 volume percent aqueous ethanol, adjusted to pH 9 with concentrated hydrochloric acid, and is applied with 25 μl of a 10 percent DHA solution in 50 volume percent aqueous ethanol; the DHA control is 50 μl of a 5 percent solution in 50 volume percent aqueous ethanol. The amine "HEDA" is 25 μl of a 2.3 percent solution of N-hexylethylenediamine in 50 volume percent aqueous ethanol, adjusted to pH 9 with concentrated hydrochloric acid, and is applied with 25 μl of an 8 percent DHA solution in 50 volume percent aqueous ethanol; the DHA control is 50 μl of a 4 percent solution in 50 volume percent aqueous ethanol. For each test, including the control, a 25 cm² area of skin is used.

In the results, "% Color Remaining" is calculated by the equation (ΔE_(RINSED) /ΔE_(UNRINSED) ×100) for the application of both amine and DHA formulations, while "Color Increase" is calculated from (ΔE_(RINSED) /ΔE_(UNRINSED)), representing the color increase over unrinsed applications of only DHA.

    ______________________________________                                                              % Color   Color                                           Amine   Subject      Remaining Increase                                        ______________________________________                                         TSPE    1            111       1.8                                                     2            102       3.6                                                     3            92        4.1                                                     4            105       3.9                                             HEDA    1            84        2.4                                                     2            82        3.2                                                     3            92        4.1                                                     4            86        2.7                                             ______________________________________                                    

These results demonstrate that: (1) skin coloration derived from both amines and DHA resists removal from exposure to water; and (2) after rinsing, up to 4.1 times more color remains on the skin at the DHA-amine sites than that at the DHA only sites. Although not shown by these data, the color formed when amine is present is within the "natural tan" area of the chromaticity plot.

EXAMPLE 12

Tests are conducted to determine the relative substantivity of color formed by the use of DHA and amine formulations of preceding Example 11. Substantivity is determined by measurement of color before and after a 10×8 centimeter, 500-gram block, fitted with a towel covering its lower surface, is pulled across the skin through five cycles, using a back-and-forth motion. This test is conducted first with the towel dry, and then with the towel saturated with water.

In all cases, DHA and amine formulations are applied to skin immediately after readings are taken with the Minolta Chroma Meter, using 25 μl of each formulation, or 50 μl of DHA control solution, on a 25 cm² skin area. A period of five hours is allowed for color development, then readings are again taken; the difference in total color is termed "Initial ΔE" for the tables which follow. After each of dry and wet rubbing, measurements are made and ΔE is again determined.

Results are as shown below, indicating that much more total color is formed in five hours when both amine and DHA are applied, as compared to only DHA applications. All results are averages for four subjects. Visually, differences in ΔE amounting to at least about 0.5 can be discerned by a trained observer.

    ______________________________________                                                   ΔE                                                             Amine       Initial     Dry       Wet                                          ______________________________________                                         TSPE        8.2 ± 1.1                                                                               8.2 ± 0.9                                                                             7.0 ± 0.7                                 DHA Control 2.8 ± 1.1                                                                               2.9 ± 1.2                                                                             2.6 ± 0.9                                 HEDA        10.4 ± 1.2                                                                              10.7 ± 1.2                                                                            8.8 ± 1.6                                 DHA Control 2.8 ± 0.3                                                                               3.1 ± 0.8                                                                             2.5 ± 1.2                                 ______________________________________                                    

These data show that: (1) much more color is formed in five hours when either of the amines is present at the DHA reaction sites; and (2) the DHA-amine color resists removal from wet and dry rubbing. After wet rubbing, about 2.7 to 3.5 times more color is present at the DHA-amine sites, as compared to DHA-only sites.

EXAMPLE 13

An experiment is conducted as in preceding Examples 11 and 12, to compare the color formation of DHA alone and DHA with a trimethylsilylamodimethicone. The amino compound used corresponds to the previously given formula for trimethylsilylamodimethicone, wherein x is about 100, y is about 32 and R is --CH₂ CH₂ CH₂ --.

Formulations for the experiment are: a 2 percent solution of DHA in 10 volume percent aqueous ethanol (the "Control"), 50 μl of which are applied to 25 cm² of skin; and a 3.1 percent solution of amino compound in water, adjusted to pH 7 with hydrochloric acid, 25 μl of which are applied to 25 cm² of skin together with 25 μl of a 4 percent solution of DHA in 20 volume percent aqueous ethanol (the "Amine+DHA").

Substantivity to water rinsing, which is determined according to the procedure of Example 11, is as follows:

    ______________________________________                                                       % Color   Color                                                  Subject       Remaining Increase                                               ______________________________________                                         1             81        5.1                                                    2             89        2.9                                                    3             87        2.2                                                    4             93        6.7                                                    ______________________________________                                    

Substantivity to wet and dry rubbing, which is determined according to the procedure of Example 12, is as follows:

    ______________________________________                                                   ΔE                                                             Formula     Initial     Dry      Wet                                           ______________________________________                                         Amine + DHA 5.6 ± 1.6                                                                               5.1 ± 1.2                                                                            3.7 ± 1.0                                  Control     2.7 ± 1.2                                                                               1.6 ± 0.9                                                                            1.2 ± 0.7                                  ______________________________________                                    

The color formed by trimethylsilylamodimethicone and DHA resists removal from water exposure and wet or dry rubbing. In addition to being substantive, the skin color after treatment closely resembles that of a natural tan.

EXAMPLE 14

An experiment is conducted using the procedure of preceding Example 11, with hairless albino guinea pigs as the subjects. The amino compound has the following structure: ##STR3## where R¹ is ethylene, R² is propylene, R³ is ethyl, R⁴ is methyl and x is about 8.

Equal volumes of a 10 percent solution of the amine in 70 volume percent aqueous isopropanol (adjusted to pH 7 with hydrochloric acid) and a 7.5 percent DHA solution in 50 volume percent aqueous ethanol are mixed just prior to application, and aliquots of 12.5 μl are applied to 6.25 cm² skin sites. Equal volumes of a DHA control (3.75 percent in 50 volume percent aqueous ethanol) are applied to adjacent sites having a similar area. After four hours, measurements are taken with the meter, the sites are rinsed under warm running water for two minutes, the sites are dried and further measurements are taken after about 30 minutes. Calculations are made using these measurements and those taken immediately before any solutions are applied.

Substantivity of skin color to water rinsing is shown by the following:

    ______________________________________                                                       % Color   Color                                                  Subject       Remaining Increase                                               ______________________________________                                         1             86        1.0                                                    2             94        1.7                                                    3             114       1.4                                                    4             95        1.8                                                    5             94        1.2                                                    6             81        1.6                                                    ______________________________________                                    

The invention has been described with respect to several specific embodiments, but is not to be limited to those embodiments, the scope of the invention being defined only by the appended claims. Various improvements, alternatives and equivalents will be apparent to those skilled in the art, and are included within the claimed invention. 

What is claimed is:
 1. Apparatus for imparting artificial tan to skin, comprising:(a) a receptacle containing a fluid formulation comprising dihydroxyacetone; (b) a receptacle containing a fluid formulation comprising a secondary polyamine; and (c) dispensing means for simultaneously or sequentially providing said fluid formulations in amounts to yield dihydroxyacetone to polyamine molar ratios about 0.1 to about
 14. 2. The apparatus of claim 1, wherein at least one of dihydroxyacetone and polyamine is present in a solution.
 3. The apparatus of claim 1, wherein at least one of dihydroxyacetone and polyamine is present in an emulsion.
 4. The apparatus of claim 1, wherein at least one of dihydroxyacetone and polyamine is present in a gel.
 5. The apparatus of claim 1, wherein there are provided molar ratios of dihydroxyacetone to polyamine about 0.5 to about
 5. 6. The apparatus of claim 1, wherein there are provided molar ratios of dihydroxyacetone to polyamine about 2 to about
 4. 7. The apparatus of claim 1 wherein at least one formulation establishes pH values about 3 to about 13, when desired amounts of the formulations are mixed.
 8. The apparatus of claim 7, wherein pH values about 5 to about 9 are established.
 9. The apparatus of claim 7, wherein pH values about 6 to about 7 are established.
 10. The apparatus of claim 1, wherein the polyamine has: (a) the formula R¹ NH(CH₂)₂ NH², in which R¹ and R² are independently hydrogen, alkyl, cycloalkyl or aromatic groups, provided that both of R¹ and R² cannot be hydrogen; (b) the formula (CH₂ CH₂ NH)_(n), where n is an integer from about 3 to about 15000; or (c) a silicone backbone.
 11. A method for imparting artificial tan to human skin, comprising contacting the skin with dihydroxyacetone and a secondary polyamine having: (a) the formula R¹ NH(CH₂)₂ NHR², wherein R¹ and R² are independently hydrogen, alkyl, cycloalkyl or aromatic groups, provided that both of R¹ and R² cannot be hydrogen; (b) the formula (CH₂ CH₂ NH)_(n), where n is an integer from about 3 to about 15000; or (c) a silicon backbone; wherein the molar ratio of dihydroxyacetone to polyamine is about 0.1 to about
 14. 12. The method of claim 11, wherein the dihydroxyacetone and polyamine are applied to skin sequentially.
 13. The method of claim 11, wherein the dihydroxyacetone and polyamine are applied to skin substantially simultaneously.
 14. The method of claim 11, wherein a formulation containing dihydroxyacetone and polyamine is applied to skin.
 15. The method of claim 11, wherein pH values between about 3 and about 13 are established as skin is initially contacted.
 16. The method of claim 13, wherein pH values between about 5 and about 9 are established.
 17. The method of claim 13, wherein pH values between about 6 and about 7 are established.
 18. The method of claim 11, wherein the molar ratio of dihydroxyacetone to polyamine is about 0.5 to about
 5. 19. The method of claim 11, wherein the molar ratio of dihydroxyacetone to polyamine is about 2 to about
 4. 20. The method of claim 1, wherein the polyamine comprises N-[3-(trihydroxysilyl)-propyl]-ethylenediamine.
 21. A composition for immediate application to skin, comprising a mixture of:(a) a formulation comprising dihydroxyacetone; and (b) a formulation containing a secondary polyamine having: (a) the formula R¹ NH(CH₂)₂ NHR², wherein R¹ and R² are independently hydrogen, alkyl, cycloalkyl or aromatic groups, provided that both of R¹ and R² cannot be hydrogen; (b) the formula (CH₂ CH₂ NH)_(n), where n is an integer from about 3 to about 15000; or (c) a silicon backbone;wherein the molar ratio of dihydroxyacetone to polyamine is about 0.1 to about
 14. 22. The composition of claim 21, wherein the polyamine has the formula R¹ NH(CH₂)₂ NHR².
 23. The composition of claim 22, wherein R¹ and R² are the same.
 24. The composition of claim 23, wherein R¹ and R² each have about 4 to about 22 carbon atoms.
 25. The composition of claim 22, wherein R¹ and R² are different.
 26. The composition of claim 22, wherein R¹ is hydrogen and R² has about 6 to about 22 carbon atoms.
 27. The composition of claim 22, wherein R¹ has about 6 to about 22 carbon atoms, and R² has 1 to about 22 carbon atoms.
 28. The composition of claim 21, wherein the polyamine has the formula (CH₂ CH₂ NH)_(n).
 29. The composition of claim 28, wherein n is no greater than about
 2500. 30. The composition of claim 29, wherein n is an integer from about 3 to no greater than about
 2500. 31. The composition of claim 30, wherein the polyamine is an amodimethicone.
 32. The composition of claim 30, wherein the polyamine is a trimethylsilylamodimethicone.
 33. The composition of claim 32, wherein the trimethylsilylamodimethicone has the formula Si(O)(CH₃)₃ --{Si(O)(CH₃)₂ }₁₀₀ --{Si(O)(CH₃)(R--NH--CH₂ --CH₂ --NH₂)}₃₂ --Si(CH₃)₃.
 34. The composition of claim 32, wherein the trimethylsilylamodimethicone has the formula Si(O)(CH₃)₃ --{Si(O)(CH₃)₂ }₂₅ --{Si(O)(CH₃)(R--NH--CH₂ --CH₂ --NH₂)}₈ --Si(CH₃)₃.
 35. The composition of claim 30, wherein the polyamine has the formula Z-{Si(O)(R⁴)₂ }_(x) --Z, in which Z is NH₂ --R¹ --NH--R² --Si(O)(OR³)₂ -- wherein R¹, R², R³ and R⁴ are independently lower alkyl having 1 to 8 carbon atoms, and x is up to about
 100. 36. The composition of claim 35, wherein R¹ is ethylene, R² is propylene, R³ is ethyl, R⁴ is methyl and x is about
 8. 37. The composition of claim 21, wherein the polyamine comprises N-[3-(trihydroxysilyl)-propyl]-ethylenediamine. 